If you require general-coverage receive capability, you should order the KBPF3 "General Coverage RX Bandpass Filter Module".
The "band pass" filters are the very first filters in the radio, they're LC filters and cover the whole band. Ham band capability comes with the "stock" K3. The KBPF3 provides band pass filter capability for other frequencies. The first IF filter, at around 8 mHz, is a crystal filter, sometimes called a "roofing filter". The K3 supports up to 5 of these in the main receiver and an additional 5 in the subreceiver. If you require FM transmit capability, you'll want the 13.0 kHz KFL3B-FM filter. I do not know if FM reception is possible with any of the other filters, but I would guess the fidelity would be very limited if it worked at all. If you require AM or ESSB transmit capability, you'll want the KFL3A-6K filter. You may receive AM with the "stock" 2.7 kHz filter that comes with the radio by tuning to one sideband. Some users prefer a wider bandwidth for improved AM fidelity and as I understand that listening to both sidebands in some situations might reduce selective sideband fading. If you're an occasional AM listener but don't need to transmit on AM, you may be fine without the 6.0 Khz AM filter. Some filters are available only in 5 pole and others only in 8 pole. The skirts are steeper for the 8 pole filters, and they're slightly more expensive. I chose 8 pole filters. I've seen data from people whose opinion I value that suggests that 5 poles are certainly enough. The performance differences are minor, but measurable. The main K3 may have up to 5 crystal filters. The main RF board filters are used for transmit as well as receive. You select the filter to be used for each mode of transmission, but the choices are limited. CW, SSB, and Data modes must use a 2.7 kHz (5 pole) or 2.8 kHz (8 pole) filter. FM transmit must use a 13 kHz FM filter. AM transmit must use a 6K AM filter. The KRX3 subreceiver may have 1 to 5 additional crystal filters. You should put filters into the KRX3 to support your dual-receive requirements. For many, that's only filters for CW and SSB. I would suggest not purchasing both the 250 hZ and 400 hZ filters. The actual widths aren't different enough. If you want both 400 and a narrower filter, I would recommend using the 5-pole 200 hZ filter for very narrow CW. You may do very well with a minimum of crystal filters, because the DSP provides selectivity down to 50 hZ. The crystal filters are useful in crowded band conditions (particularly contests). Narrow crystal filters help most when the desired signal is very near a very loud interfering signal, and by using a narrow crystal filter you can bring the desired signal inside the crystal filter passband and the undesired signal outside. If you plan to use your KRX3 for "diversity", there are advantages to having the crystal filters match one another. 8 pole filters are recommended here because the 5 pole filters have a "frequency offset" that you would prefer to have match. Elecraft will provide matched pairs of 2.7 kHz 5 pole filters. But it's only slightly more to get two 8 pole 2.8 kHz filters that have no frequency offset. You can always add filters at a later time; you might consider using the radio a while before filling it up with filters that you're not sure you need. I didn't do this myself, but it seems like a good idea to me. Dick, K6KR -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Rich Sent: Saturday, August 16, 2008 10:48 AM To: elecraft@mailman.qth.net Subject: [Elecraft] K3 Configuration Cookbook? I have tried searching the Elecraft WebPages and manual and can not find complete ,concise, information as to the minimum required components (above the basic K3) for each of the various different modes. Is this posted somewhere or can someone provide a cookbook of "recipes" for each of the various different non "Basic" modes (e.g. FM, AM, SWL, etc.)? Should include Basic K3 and additional requirements for KRX3. Do I need 8 pole filters on both? Thanks, Rich, KE0X -- View this message in context: http://n2.nabble.com/K3-Configuration-Cookbook--tp728066p728066.html Sent from the Elecraft mailing list archive at Nabble.com. _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
